An aircraft engine represented by a gas turbine engine incorporates a heat exchanger. A heat exchanger for an aircraft engine is used to cool the lubricant in the aircraft engine and cool the lubricant in a generator incorporated in the aircraft engine. Examples of the heat exchanger for an aircraft engine include a plate-fin-type heat exchanger, a shell-and-tube-type heat exchanger, and a surface-type heat exchanger.
Among the heat exchangers described above, the surface-type heat exchanger can be made compact as compared with the other heat exchangers. Such a surface-type heat exchanger is proposed, for example, in Japanese Patent Application Publication No. 2008-144752 (Patent Literature 1) and Japanese Patent No. 5,442,916 (Patent Literature 2).
The surface-type heat exchangers disclosed in Patent Literatures 1 and 2 each have an arcuately-curved-plate-like shape. The heat exchanger is disposed along a curved surface of an aircraft engine. The curved surface of an aircraft engine is, for example, the inner or outer circumferential surface of a fan case or an engine core casing. More specifically, the surface-type heat exchanger is disposed, for example, on the inner circumferential surface of the fan case or the outer circumferential surface of the engine core casing. The surface-type heat exchanger has a curved shape curved along the curved surface of the location where the heat exchanger is disposed.
The surface of the surface-type heat exchanger is exposed to an air flow passing through the aircraft engine. A plurality of heat dissipating fins are disposed on a surface of the surface-type heat exchanger. The plurality of heat dissipating fins extend in the direction of the axis of rotation of the aircraft engine and are arranged in the circumferential direction of the aircraft engine. The heat exchanger further has an internal channel.
A fluid, such as the lubricant described above, (hereinafter referred to as target fluid) flows into the surface-type heat exchanger and flows through the internal channel. The plurality of heat dissipating fins on a surface of the surface-type heat exchanger are exposed to the air flow. The heat of the target fluid in the channel is therefore dissipated to the outside via the heat dissipating fins. The cooled target fluid flows out of the heat exchanger and returns to an apparatus where the target fluid is used (such as generator).
As described above, the surface-type heat exchanger is disposed along an arbitrary curved surface of an aircraft engine. Resistance of the air flow flowing through the engine is therefore smaller than the resistance in the other heat exchangers.
In a surface-type heat exchanger, a plurality of heat dissipating fins arranged on a surface of the heat exchanger extend along the axis of rotation of an aircraft engine, as described above. The heat dissipating fins of each of the surface-type heat exchangers disclosed in Patent Literatures 1 and 2 described above also extend along the axis of rotation of the aircraft engine. In this case, the heat exchange efficiency is maximized when the air flow flowing along the heat dissipating fins flows along the axis of rotation. In an aircraft engine, however, for example, an air flow, when it passes through a fan, is converted into a swirl flow. The swirl flow does not flow along the axis of rotation but flows in a direction that intersects the axis of rotation. Accordingly, the direction in which the heat dissipating fins extend intersects the air flow (the swirl flow). In this case, a high heat exchange ratio is unlikely to be achieved.